feat(lang): bind a port member that takes nothing to a variable

bind Purse { money: g_money } writes the getter bind_Purse_money in the
bind's own file, so a one-line wrapper per member is not needed; a
member that takes something is refused a variable. Reseed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

changes/bind-variable.md

@@ -0,0 +1,5 @@
+bump: minor
+type: feature
+**`bind Purse { money: g_money }` - a port member bound to a variable.** A member that takes nothing
+may name a global instead of a function; the compiler writes the getter in the bind's file, so the
+one-line wrapper is gone. A member that takes something is refused a variable.